1. Field of the Invention
The present invention relates to an image exposure apparatus which winds a photosensitive material on a peripheral face of a rotating drum or the like and scanningly exposes the photosensitive material.
2. Description of the Related Art
In general, for printing, a photosensitive lithographic printing plate (hereafter, referred to as a printing plate) is employed in which a photosensitive layer is formed on a sheet-like support such as an aluminum sheet. Such a printing plate has a size (length and width) which corresponds, for example, to the size (length and width) of a print.
Among image exposure apparatuses that expose an image on a printing plate, there is one in which a printing plate is wound around a rotating drum, and by irradiating a light beam according to image data onto the printing plate while rotating the printing plate together with the rotating drum, the printing plate is scanningly exposed.
Even in this type of image exposure apparatus, it is necessary to precisely form an image at a predetermined position of the printing plate. Thus, among image exposure apparatuses, for example, there is one in which a puncher is provided, a notch for positioning is formed at a tip of the printing plate by the puncher, and a pin for positioning provided in a protruding condition on a peripheral surface of a rotating drum enters the notch when the printing plate is wound around the rotating drum so as to position the printing plate.
In order to position the printing plate on the rotating drum precisely, it is necessary to precisely position the printing plate with respect to the puncher.
In general, for positioning the printing plate, the printing plate is placed on a table for positioning and is moved in a vertical direction and in a horizontal direction so as to abut the pin for positioning. However, in order to implement this type of positioning, it is necessary to provide a table whose size is larger than that of the printing plate. Thus, the apparatus becomes quite large-sized. Further, it is necessary to remove the printing plate whose positioning is finished from the table and wind around the rotating drum. Thus, a transport mechanism for this operation is necessary.
As a method for positioning the printing plate, a method has been devised wherein the printing plate is sucked by a sucker so as to make the plate abut a positioning pin. However, in this positioning method, it is necessary to reduce transport speed at the time when the printing plate abuts the positioning pin or to reduce suction of the sucker or both, in order to implement precise positioning while preventing damage to the printing plate. When the transport speed of the printing plate is reduced, exposure processing time becomes long, and rapid processing becomes difficult. In order to decrease the suction of the sucker acting on the printing plate, a high cost, complex switching mechanism is needed.
The present invention has been developed considering the facts described above, and an object of the present invention is to present an image exposure apparatus having a simple structure in which a photosensitive material to be wound around a rotating drum can be reliably positioned in a small space.
In an image exposure apparatus according to a first aspect of the present invention, positioning of a sheet-like photosensitive material at a rotating drum is enabled by positioning the photosensitive material at a predetermined position before the photosensitive material is wound onto a peripheral surface of the rotating drum in order to be scanningly exposed, and the image exposure apparatus includes: a transport device which imparts transport force to each of two end portions in a width direction of the photosensitive material, which width direction is perpendicular to a transport direction of the photosensitive material, and transports the photosensitive material while maintaining the photosensitive material in a state in which the photosensitive material is tilted at a predetermined inclination; a first positioning device which stops each of two end portions in the width direction of a leading end of the photosensitive material, which is being transported by the transport device, at a predetermined position; a moving device which moves the transport device and the photosensitive material integrally along the width direction of the photosensitive material after the photosensitive material has been stopped at the predetermined position by the first positioning device; and a second positioning device which stops the photosensitive material, which is moved by the moving device, at a predetermined position.
The transport device imparts the transport force to both respective side edges in the width direction of the photosensitive material, such as a printing plate, to transport the photosensitive material in the state in which the photosensitive material is tilted at a predetermined inclination. The first positioning device stops both end portions in the width direction of the leading end of the photosensitive material transported by the transport device so that both end portions are at predetermined positions. Thus, the photosensitive material is positioned with respect to the transport direction.
The moving device moves the transport device along the width direction of the photosensitive material such that the photosensitive material is moved integrally therewith along the width direction. The second positioning device stops the photosensitive material moved by the moving device at a predetermined position, so as to implement positioning along the width direction of the photosensitive material.
When positioning is implemented with respect to the transport direction and the width direction perpendicular to the transport direction as described above, because the photosensitive material is tilted, positioning can be implemented in a smaller space than positioning the photosensitive material in a horizontal state, whereby an installation space for the apparatus can be made smaller. Further, since positioning of the photosensitive material is implemented on the transport device, transporting the photosensitive material whose positioning is finished can be easy.
In the image exposure apparatus of the present invention, preferably, the transport device includes: a plurality of transport belts provided substantially perpendicular to the direction in which the photosensitive material is transported, with the transport belts being disposed at predetermined intervals along the width direction of the photosensitive material; and a transport roller provided substantially perpendicular to the direction in which the photosensitive material is transported, and with the transport roller disposed to face each of end portions in the width direction of the photosensitive material, the transport roller pinches the photosensitive material between the transport belts and the transport roller and to impart a transporting force to the photosensitive material. Further, preferably, the transport roller is divided into a plurality of rollers along a direction substantially perpendicular to the transport direction of the photosensitive material. The plural rollers obtained by dividing the transport roller are preferably mutually relatively rotatable.
By providing rollers opposed to both respective end portions of the width direction of the photosensitive material, the end portions of the width direction of the photosensitive material can be separately held and can be imparted with transport force between the respective rollers and the transport belts.
Even when one end portion side of the width direction of the photosensitive material has been stopped at the predetermined position by the first positioning device, by moving the other end portion side of the photosensitive material, skew with respect to the transport direction of the photosensitive material can be readily remedied.
In the image exposure apparatus of the present invention, the transport device preferably includes a winding device that winds the photosensitive material around the roller and feeds the photosensitive material toward the transport belts, and the moving device preferably moves the winding device and the transport belts integrally.
Thus, since positioning of the photosensitive material can be implemented in a state in which a leading end side of the photosensitive material is tilted on the transport belt and a trailing end side of the photosensitive material is wound around the roller, positioning can be implemented in an extremely small space, even for a photosensitive material whose length along the transport direction is long, and the apparatus can be made compact.
The image exposure apparatus of the present invention preferably further includes at least one cassette which accommodates the photosensitive material. The winding device preferably moves horizontally along the transport direction. The transport device preferably adjusts an angle thereof interlocking with the horizontal movement of the winding device. The winding device preferably has a guide plate that guides the photosensitive material toward the transport device. This guide plate preferably adjusts an angle thereof interlocking with the horizontal movement of the winding device.
Various sizes of photosensitive materials can be combined, depending on service conditions, and further the winding device moves horizontally along the transport direction, whereby photosensitive materials can be supplied from the plurality of cassettes by one apparatus. The transport device and the guide plate adjust their angles in response to the horizontal movement of the winding device such that not only can the photosensitive material be smoothly supplied but also the apparatus can be made compact.
In the image exposure apparatus of the present invention, the winding device preferably has a plurality of winding belts arranged at predetermined intervals along an axial direction of the roller such that the photosensitive material is pinched by the roller and the winding belts, and fed out.
The plurality of winding belts are arranged along the axial direction of the roller that winds the photosensitive material, and the photosensitive material is pinched between the roller and the winding belts, whereby both side edges of the width direction of the photosensitive material can be individually held, and movement of the trailing end side of the photosensitive material becomes easy when a skew with respect to the transport direction of the photosensitive material is being remedied by the first positioning device.
The image exposure apparatus of the present invention preferably further includes a puncher that forms a notch for positioning in the photosensitive material. Further, the rotating drum preferably has a pinch device that detachably fixes the photosensitive material on the rotating drum. Moreover, the transport device preferably transports the photosensitive material toward the puncher or the rotating drum or both in a state in which the photosensitive material is moved in the width direction by the moving device.
At this time, since the transport device is moved together with the photosensitive material integrally by the moving device, the transport direction of the photosensitive material is not skewed by the transport device. Thus, the photosensitive material whose positioning is finished can be fed out without occurring dislocation. By providing a notch for positioning in the photosensitive material and providing the pinch device that detachably fixes the photosensitive material to the rotating drum, positioning time of the photosensitive material can be shortened and positioning accuracy can be improved.